Build the Water Molecule
Combine hydrogen and oxygen atoms to form H2O
What this lesson covers
Why it matters
Imagine a molecule so familiar that, in a single day, you meet it as solid ice, flowing liquid, and invisible vapour.
Predict first
If you break a water molecule apart, what atoms do you find inside?
Water is a compound with the formula H₂O, meaning exactly two hydrogen atoms bond to one oxygen atom.
- Two hydrogen atoms and one oxygen atom — correct
- One hydrogen atom and two oxygen atoms
- Two hydrogen atoms and two oxygen atoms
- One water atom
What you do
Build water by crossing valencies — one oxygen (valency 2) snaps onto two hydrogens (valency 1) to make H2O.
Check yourself
Why is water (H₂O) classified as a compound and not an element?
Elements consist of only one type of atom. Compounds like water consist of two or more different elements chemically combined.
In the formula H₂O, what does the subscript '2' indicate?
Subscripts in a chemical formula indicate the number of atoms of the preceding element. H₂ means two hydrogen atoms.
- It is made of two different types of atoms chemically bonded — correct
- It is a liquid at room temperature
- It can be found in nature
- There are two hydrogen atoms for every one oxygen atom — correct
- There are two oxygen atoms
- The molecule weighs twice as much as oxygen
- There are two water molecules